Devices used to produce an air curtain, sometimes also termed air knives, typically comprise a chamber connected to a source of pressurized air, from which chamber air is discharged to the ambient atmosphere through an elongate opening. The air curtain is directed towards a surface that moves relative to it, the air in the air curtain usually traveling in a direction normal to the surface. The air curtain may serve different purposes such as drying the surface, blowing away debris, confining material on the surface of a conveyor, removing or controlling the thickness of an applied liquid layer and separating particles by size. Such air curtains are typically characterized by high exit air flow which in turn creates a high intensity of impact air onto the surface towards which the compressed air is directed.